Static hearing refers to the hearing ability represented by a conventional 2-dimensional audiogram obtained through hearing tests performed at specific times in specific environments for various frequencies. In an audiogram-based method of outputting audio signals employed in a conventional multi-channel digital hearing aid, etc., the static hearing values obtained at specific times in specific environments are used as a basis for determining the output level for each frequency band.
The procedure for deciding the output level for each frequency band may be referred to as “fitting”. In an existing static hearing-based method of outputting audio signals for each frequency band, the hearing tests and the fitting may be separated procedurally.
A conventional static hearing-based method of controlling audio output may include the steps of finding the hearing threshold for each frequency, adjusting the output of audio signals for each frequency band using the hearing thresholds thus found (i.e. fitting), and outputting the audio signals.
FIG. 1 illustrates a static hearing-based method of controlling audio output for each frequency according to the related art.
FIG. 1(a) illustrates the output levels of hearing thresholds found by the hearing test step, where the X axis represents frequency or frequency band, and the Y axis represents audio output level.
As one of the most popular methods used for a hearing test, the pure tone audiometry method, which finds the hearing thresholds by using the frequency characteristics of auditory cells, is widely being used as an internationally standardized hearing test method.
FIG. 1(b) illustrates the output levels of audio signals after adjusting the outputs for each frequency band. In FIG. 1(b), it can be seen that the audio output for each frequency band is adjusted based on static hearing by using the threshold of hearing values for the respective frequencies.
FIG. 1(c) illustrates the output levels of the audio signals as they are actually outputted.
However, considering the existing scientific fact that a person's hearing ability for each frequency can actually change when the person is exposed for a certain period of time to a sound conditioning environment for each frequency band at the hearing threshold level, it can be said that the conventional methods of controlling audio signal output based on static hearing overlook the inherently dynamic quality of a person's hearing ability.
That is, the conventional method of outputting audio signals for each frequency band based on static hearing does not consider the dynamic changes in hearing thresholds resulting from improvements in the user's hearing.